Tanning composition



UNITED STATES PATENT rricn,

GEORGE HENRY RUSSELL, OF NEXVBURG, PENNSYLVANIA.

. TANNING COMPOSITION.

SPECIFICATION forming part of Letters Patent No. 411,931, dated October 1, 1889. Application filed March 7, 1888. Serial No. 266,462. (No specimens.)

To all whom it may concern/.-

Be it known that I, GEORGE HENRY Rus- SELL, a citizen of the United States, residing at Newburg, in the county of Cumberland and State of Pennsylvania, have invented certain new and useful Improvements in Chemical Baths for Preparing the Hides of Animals, &c.; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Thisinvention relates to a chemical compound for preparing the hides of animals and furs for any process of bark or extract tanning with or without the usual process of bating or depleting thehides in a manure or other bate, with or without the use of salt in the liquors during the process of tanning, and for the purpose of causing the bark or extract liquors to be absorbed more rapidly by the hide during the process of tanning it into leather, and for the purpose of preventing the rapid formation of gallic acid, and retanning imperfectly tanned stock, and softening leather that is hard and cracky.

My invention consists of a bath or compound which is to be used for preparing the unhaired raw hide to be converted into leather, with bark or bark extract liquors, producing a leather of an exquisite fineness of grain, pliability, strength, and toughness of the fiber with a good fair color. It is also to be used on the ground bark in the leaches and in the liquors for the purpose of preventing the rapid formation of gallic acid. It is also to be used for retanning imperfectlytanned leather.

In preparing the bath for seventy-five or one hundred hides I take water (700 gallons) seven hundred gallons. To this add threefourths or one bushel of salt. Agitate the solution with a plunger until the salt is well dissolved. Then test its specific gravity with a barkonieter. If the solution is too weak, add more salt until the barkometer shows 4 or 5. 4 is for a weak solution and 5 for a stronger one. To the above solution add fort-y orfifty pounds of soda. Any kind of soda will do; but the bicarbonate of soda is to be preferred.

Agitate the solution with a plunger. Then test its specific gravity with the barkometer. Add soda until it shows 8 or 10. The 8 is for a weak solution of the bath, and 10 a strong solution of it. To the above solution add two and one-half gallons of sulphuric acid, (oil of vitriol,) spreading the acid evenly over the surface as it is poured in. Then take a plunger and agitate the mixture thoroughly while it is effervescing and until it has ceased to effervesce. Then testits specific gravity with a barkometer. For a weak solution of the bath the barkometer should show about 10, or 12 for a strong solution of it. The weaker solution is for light hides and the stronger solution forheavy hides.

The ingredients in the above compound should be proportioned so that the acid in the solution will not be in excess. It should be either neutral or alkaline. If the acid should be in excess, the intended results of the solution would be destroyed. W'hen plump leather is to be made, the solution should be neutral. When a leather of asofter texture and finer grain is to be made, the solution should be alkaline, or the soda in excess. If the coinpouud or chemical bath is used as an antiacid on the ground bark or in the liquors to prevent the rapid formation of gallic acid and to promote a rapid absorption of the bark liquors, it should be alkaline.

The chemical bath is now ready to receive the raw unhaired hide, in which it is to be prepared for tanning it into leather, which is done as follows: After the'hide has been limed and unhaired, itis the general custom to immerse it in a bath of chicken, bird, or dog dung, so that whatever lime may be in the hide is neutralized by the ammonia that is in the manure. It also depletes and softens the hide. The raw unhaired hide can be treated in the above or other bate in the usual way before it is immersed in the chemical bath; but I prefer that the above process of bating and neutralizing and softening of the hide be omitted entirely, and in lien or instead thereof the hides be worked out of warm or cold Water once or twice over the beam be fore they are immersed in the chemical bath.

The usual process of bating can be used in combination with the chemical bath; but better results can be obtained in the leather tanned by omitting the bating or neutralizing of the lime process altogether. After the hides have been worked out of cold or warm water over the beam they are then ready to be immersed in the chemical bath,wherethey are prepared to receive the tan-liquors. When the hides are put into the chemicalbath reel or handle them five or six times a day. Light hides and skins should be kept in the bath one and a half to two days, and heavy hides two to three days.

When the hides are in the bath, it will be observed that a chemical change takes place on the grain and in the fiber of the hides. The grain becomes coated over with a slime. This slime is greater when the bath is alkaline than when it is neutral. It is this slime that is formed on the grain that causes the grain to be made fine and close. Therefore the bath should be either neutral or alkaline.

To make a leather of more plumpness and of a medium-fine grain, the bath should be neutral. To make a leather of extra fineness of grain and fiber, the bath should be alkaline. The hide is opened up while in the bath. It is softened and toughened, and its chemical conditions are so changed that it has a stronger affinity for the bark-liquors. The natural acids that are in the pores of the hide being neutralized by the bath, it causes it to tan more rapidly.

The hides having been prepared in the bath are now ready to go into the liquors to be tanned into leather as follows: Put the hides into a weak sweet liquor of about 5 to 8 barkometer test. Reel or handle them in this liquor until they are well colored.

If weight is an object, the hides should be plumped in the usual way and tanned in strong liquors; but to make a fine grade of leather the plumping process should be omitte The hides can now be tanned out byhandling them in good sweet liquors graded from to barkometer test. If the lay-away or hanging-in plan is adopted, change the liquors on them every five or ten days. It will be observed that the hides tan very fast,

saving much time and labor.

To prevent the rapid formation of gallic acid in the liquors, put a few gallons of the chemical bath into the liquors during the process of tanning-that is, to a vat of about seven or ten hundred gallons of liquor.

It is the custom with some tanners to use salt in the strong liquors for the purpose of making increased weight in the leather and for increasing the specific gravity of the liq- Salt can be used in the liquors in combination with the treatment of the' hides in the chemical bath; but as it makes the leather porous and adds a fictitious weight We do not recommend its use in the liquors, except it might be for tanning lining-skins andgloveleather.

The use of salt in the liquors is not new, and we do not claim its use, except in the above combination with the chemical bath.

After the hides have been run through the chemical bath and its strength is reduced it is worth its original cost to use it on the ground bark as a Water-leach and for the prevention of the formation of gallic acid so rapidly.

It is wellknown that the hides of the warmblood fishesnamely, the whale and porpoise that inhabit the salt-Waters of the oceans make amuch finer grained and tougher leather than can be made from the hides of the warm-blood animals that inhabit the dry land. The toughness of the hides of the warm-blooded fishes is caused by the elements that constantly surround the fish and the exudation of acid through the pores of the skin. It is this exudation of the acid upon the elements that surrounds the porpoise that causes a slime to form upon its hide, forming a fine grain. It is this chemical action upon the hides of these fishes that toughens them.

An analysis of the salt-water of the ocean shows that it is composed of soda, salt, carbonic acid, and a little lime. In my chemical bath I have the same component partsnamely, soda, salt, carbonic acid, and a little lime-in the hide. By the lime not being neutralized in a bate and the sulphuric'acid (in the minority) to correspond with the acid that is exuded through the pores of the skin of the fish I obtain corresponding results upon the hide that is immersed in the bath -namely,

toughness of fiber and fineness of the grain.

I madethis natural process of the formation of toughness in the hides of the warm-blood fishes my guide in inventing the chemical bath, and this is wherein my discovery of the chemical bath for preparing hides for tanning, &c.,is founded.

,When the chemical bath is used for preparing furs for tanning, it gives to them a toughness and softness that is hardlyto be attained by any other process of bark-tanning.

The use of the chemical bath as an antiacid to prevent the rapid formation of gallic acid, which is always a loss to the tanner, produces great savings of bark. f

To retan leather that is imperfectly tanned and to soften and toughen leather that is hard, first scour it well, then put it into the bath for twelve to twenty-four hours. Then tan it out by handling it in a strong liquor.

The usual time taken to tan leather that is processed in this chemical bath-that is, in the liqu or-is, for calf-skins, thirty days; hips and light hides, thirty-five to sixty days; heavy hides, sixty days to one hundred and twenty days, according to the strength of the liquors used.

Iio

Having thus described my invention, whatI In testimony whereofI afiix my signature in claim, and desire to secure by Letters Patent, presence of two witnesses.

iS- r The herein-described compound for tan- GEORGE HENRX L 5 ning, composed of bark, bicarbonate of soda, \Vitnesses:

salt, sulphuric acid, and Water, in about the SAML. E. KELSO, proportions specified. W. KIKELSO. 

